﻿The function gets the set of <i>IfcPhysicalQuantity</i>'s.
It iterates through the <i>Name</i> attibute of the <i>IfcPhysicalQuantity</i>'s
and verifies that no <i>Name</i> appears twice.
<blockquote>
  <p>
    <span style="font-size:smaller;color:blue">HISTORY&nbsp; 
    New function in IFC2x4</span>
  </p>
</blockquote>